Indicating flashlamp

ABSTRACT

A flashlamp in an enclosing envelope, such as a flashcube having a plastic cover, with a substance which will product a protuberance on said envelope as a result of the flash. In this way, a used flashlamp can be detected by the feel of the protuberance, without the operator&#39;&#39;s having to look at the lamp or cube itself. The substance can be a material which generates heat or explodes on being subjected to other heat or radiation. A mixture of potassium chlorate with lactose, or with sulfer can be used, or thermit or other suitable materials. An ignitor and an exothermic material, or a sugar with an oxidant can be used.

United States Patent I151 3,676,663

Beare et a1. [4 July 11, 1972 s41 INDICATING FLASHLAMP FOREIGN PATENTS OR APPLlCATlONS [72] Inventors: Gene K. Beare, Darien, Conn; Bernard 255,897 7/ 1967 Austria ..240/1.3

Kopelman, Salem, Mass; Donald E. Seeger, Succasunna, NJ. Primary Examiner-Samuel S. Matthews Assistant Examiner-Fred L. Braun [73] Assume: Sylvan Electric Products Attorney-Norman J. O'Malley and Laurence Burns [22] Filed: Jan. 21, 1969 l N 792 3 4 [57] ABSIRACT 21 A l l 1 pp 0 A flashlamp in an enclosing envelope, such as a flashcube having a plastic cover, with a substance which will product a [52] U.S. Cl. ..240/L3, 116/114 V, 264/230 protuberance on said envelope as a result of the flash. In this [51] Int. Cl. ..G03b 15/02 way, a used flashlamp can be detected by the feel of the protu- [58] Field of Search ..240/ 1 .3; 95/ 1 1; 1 16/1 14.19, er n Without the operator's having to look at the lamp or 1 16/1 14.20; 264/230, 342 cube itself. The substance can be a material which generates heat or explodes on being subjected to other heat or radiation. [56] References m A mixture of potassium chlorate with lactose, or with sulfer can be used, or thermit or other suitable materials. An ignitor UNITED STATES PATENTS and an exothermic material, or a sugar with an oxidant can be used. 3,223,526 12/ 1965 Grieshaber et a1 ..264/230 X 3,380,357 4/1968 Harvey ..240/ 1.3 X 6 Claims, 4 Drawing figures il lm t PATENTEDJUL 1 1 I972 GENE K. BEARE llllm.

BERNARD KOPELMAN DONALD E. SEEGER INVENTORS TTORNEY INDICATING FLASHLAMP FIELD OF INVENTION This invention relates to flashlamps, especially those used for photography. In particular, it relates to a flashlamp in a plastic envelope, and especially to a group of flashlamps enclosed in a surrounding plastic envelope to form a unit, in which one lamp can be flashed at a time. Such devices are now well known in the art and are generally called flashcubes.

SUMMARY OF PRIOR ART The usual commercial flashcube has four flashlamps with a transparent cubical plastic envelope around them, the envelope having a plastic cover and a base which closes off the bottom of the cube. In such units, it is sometimes difficult to tell whether a particular lamp in the unit has been flashed, especially in a dimly-lighted room, where the flashlamp is used to provide the light needed for photography. Moreover, if a person puts a flashcube in a camera, takes four pictures and counts them, he knows he must then change to a new flashcube. But if he hasnt kept count, or takes only one or two pictures and then removes the flashcube for convenience, and reinserts it some time later when needed, he needs to known which lamps were used previously and which are the unused ones. It is important for him to know that the next flashlamp he uses will be a good one.

The use on the interior of the flashlamp of a dot of material which changes color, for example, from blue to red, when a leak in the flashlamp admits air to the bulb, is of course well known. This merely tells whether or not the flashlamp will be effective when flashed, but not whether it has already been flashed.

For the latter purpose, a changeable colored dot has also been suggested, but this requires that the operator look carefully at the face of the cube before snapping the shutter to take a picture. When this is difficult to do without losing the chance for a picture, or in a dimly lighted room, the colored dot is ineffective.

BRIEF SUMMARY OF INVENTION To eliminate such difficulties, we have discovered that a spot of material which, though it may not change color, will produce a small lump, protuberance or some sort of roughness on the face of the plastic cover of the flashcube, is very effective. The operator can feel the protuberance or absence of it with his finger without taking his eyes off the subject to be photographed, and will know at once, without even looking at the cube, that the bulb in position has not been flashed.

The production of such a protuberance can be effected by the use of a material which will explode or heat a small portion of the plastic face of the cube when activated by the heat or light from the flash. A small dot of the material is sufficient and may be located either on the face of the cube or on the lamp depending upon the particular composition.

We have discovered that the desired results can be achieved in several ways. In the first, the dot consists of two portions, one an ignitor and the other an exothermic material. Placed against the inner face of the cube is a dot of Thermit mixture consisting of magnesium or aluminum as the reductant, and iron oxide or sodium nitrate as the oxidant in intimate mixture with the reductant. Over this is placed a very thin dot of the ignitor, which may be a mixture of magnesium powder and barium peroxide. The barium peroxide-magnesium mixture is apparently very sensitive to both heat and light.

We have also found that the magnesium itself can be set off even without an oxidant mixed therein. To assure ignition, the magnesium may be mixed with barium nitrate, potassium chlorate, barium peroxide or ion oxide.

The two embodiments mentioned above appear to depend upon the sensitivity to actinic light to initiate the reactions. As such. the dots may be placed on the inner face ofthe cube. For a reaction involving thermal activation, the dot is preferably placed on the face of the lamp. Generally, organic fuels or reductants are needed for this thermal activation; thus, mixtures of potassium chlorate with lactose will ignite as low as C. Other sugars and other oxidants, such as potassium perchlorate and potassium nitrate, require higher temperatures. In addition, a mixture of sulphur and potassium chlorate ignites at the low temperature of 220 C.

Further increases of sensitivity of ignition can be achieved by the use of reductants sensitive to oxidation, such as finely divided titanium, pyrophoric iron or cerralloy.

The most desirable embodiment for a particular device can be determined by factors such as controllability of the heat evolved, the uniformity of the application of the dot, the relative desirability of placing the dot on the lamp or the cube. and the desirability of avoiding a "powder burn" appearance after ignition, and other factors, although the latter does not affect the light output from the flash. Control of the heat can be effected somewhat by the addition of inert substances, such as silica, or by varying the ratio of the reducing and oxidizing materials.

For best results, the amount of material used should be sufficient to form a protuberance but not enough to blow or melt a hole through the plastic face of the flashcube. As stated before, the forming of a protrusion on a face of the plastic envelope of the flashcube can also be achieved by the use of heat-generating material on the bulb of the flashlamp itself, so that the hot material from the exotherm will reach the proper face of the cube and cause a lump, protrusion or rough spot upon it. The material can be placed on the front part of the bulb, in register with the flashcube face in front of that bulb.

At the time of the flash, the dot of exothermic material is present on the bulb only as a bit of diffusing material, which does not appreciably decrease the amount of light from the bulb.

Other objects, features and advantages of the invention will be approved from the following specification, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a perspective view of a flashcube, showing the relative location of an indicator spot on each face of the cube.

FIG. 2 is an elevational view of the flashcube showing an unfired lamp and an adjacent face of the cube after firing.

FIG. 3 is a top view of the cube partly in section showing an unfired lamp with its indicator spot and a fired lamp with its deformed face.

FIG. 4 is a similar view of another embodiment of the inventton.

In FIG. I, the flashcube 1 has a cubical plastic cover 2 with its otherwise open bottom closed by the plastic base 3 of the type customary in the art. The protruding annular portion 4 of the base 3 is shown in more detail in FIG. 2, and has the wire contacts 5 held by it, and the extending center pin 6 which fits into a suitable socket in the usual manner. The cover has the top 12.

The customary reflectors 7, having the portion 8 of somewhat different curvature than the remainder, are in place around the sides and back of each flashlamp 9.

A dot 10 of powdered material is present on the inside surface of a face 11 of the plastic cover, in the path of light and heat from a flashlamp 9. Such a dot 10 is preferably present on all four faces of the flashcube, and consists, in one example, of a powdered mixture of 35percent lactose, 55percent potassium chlorate and 10 percent manganese dioxide. About 50 milligrams of the mixture were used per lamp, that is per dot, and was applied in a lacquer of a Spercent solution of cellulose nitrate in acetone. About 0.15 cc. of the lacquer was used for 200 milligrams of the powdered mixture. The dot was about one-eighth inch diameter.

Before and during the flash, the dot 10 is a small diffuse coating, which does not substantially reduce the light emitted .by the flashcube. After flashing, the plastic cover may be black or discolored, but since the discoloration is not present during the flash, it does not affect the light output. The face of the flashcube is smooth before flashing, as shown by the face at the left-hand side of FIG. 2; after flashing, there is a protucube 1 with the fingers. It is unnecessary to look at the flash cube or flashlamp to determine whether or not a particular one is flashed.

In FIG. 3, the dot'l0 is shown on the inside surface of face 11, with a protuberance 13 on the face corresponding to a flashed lamp.

A top view of a flashcube in which a dot I4 is present on unflashed lamp 15 in the flashcube l, with no dot on the plastic face 11 of the cube, is shown in FIG. 4. After flashing, the protuberance 17 is present on the face 11 of the flashcube. In this case, the dot was made of the same coating of potassium chlorate and lactose previously described, although other mixtures could be used.

Instead of a protuberance 13 or 17, the flashing could be arranged to produce a depression in the outer face, which could also be felt by the operator. Any roughening of the surface, such as wrinkling, would give an indication.

While we have described certain specific embodiments of the invention, other embodiments and modifications will be apparent, from the foregoing description, to a person skilled in the art, without departing from the spirit and scope of the invention as defined in the claim.

What we claim is:

l. A photographic flash unit comprising a series of flashlamps, a light-transmitting plastic envelope enclosing said series of lamps and having a region associated with each flashlamp through which light can emerge from said flashlamp, and means comprising a heat sensitive material, actuated by the flashing of a flashlamp, to produce a local deformation of the outer surface of said plastic envelope in the region associated with that flashlamp.

2. The unit of claim 1 in which the means is a mixture of materials capable of causing a highly exothermic reaction when ignited, said material being in proximity to the inside surface of said plastic envelope.

3. The combination of claim 2, in which the material is a combination of thermit and a barium peroxide ignitor.

4. The unit of claim 1, in which said heat generating material is present on the outer surface of said flashlamp.

5. The combination of claim 4, in which the material is potassium chlorate and lactose.

6. The combination of claim 1 in which the enclosing plastic envelope is a cube with its bottom face closed by a base for attachment to a camera, and the series of flashlamps is arranged with one flashlamp in register with each face, and a reflector for each flashlamp to direct light from its flashlamp to the corresponding face. 

2. The unit of claim 1 in which the means is a mixture of materials capable of causing a highly exothermic reaction when ignited, said material being in proximity to the inside surface of said plastic envelope.
 3. The combination of claim 2, in which the material is a combination of thermit and a barium peroxide ignitor.
 4. The unit of claim 1, in which said heat generating material is present on the outer surface of said flashlamp.
 5. The combination of claim 4, in which the material is potassium chlorate and lactose.
 6. The combination of claim 1 in which the enclosing plastic envelope is a cube with its bottom face closed by a base for attachment to a camera, and the series of flashlamps is arranged with one flashlamp in register with each face, and a reflector for each Flashlamp to direct light from its flashlamp to the corresponding face. 